/seo-hreflang

name: seo-hreflang
description: >
  Hreflang and international SEO audit, validation, and generation. Detects
  common mistakes, validates language/region codes, and generates correct
  hreflang implementations. Use when user says "hreflang", "i18n SEO",
  "international SEO", "multi-language", "multi-region", or "language tags".
user-invocable: true
argument-hint: "[url]"
license: MIT
metadata:
  author: AgriciDaniel
  version: "2.3.1"
  category: seo

Hreflang & International SEO

Validate existing hreflang implementations or generate correct hreflang tags for multi-language and multi-region sites. Supports HTML, HTTP header, and XML sitemap implementations.

Validation Checks

1. Self-Referencing Tags

• Every page must include an hreflang tag pointing to itself
• The self-referencing URL must exactly match the page's canonical URL
• Missing self-referencing tags cause Google to ignore the entire hreflang set

2. Return Tags

• If page A links to page B with hreflang, page B must link back to page A
• Every hreflang relationship must be bidirectional (A→B and B→A)
• Missing return tags invalidate the hreflang signal for both pages
• Check all language versions reference each other (full mesh)

3. x-default Tag

• Recommended when a selector/fallback URL exists: designates the fallback page for unmatched languages/regions
• Typically points to the language selector page or English version
• Only one x-default per set of alternates
• Must also have return tags from all other language versions

4. Language Code Validation

• Must use ISO 639-1 two-letter codes (e.g., `en`, `fr`, `de`, `ja`)
• An **optional ISO 15924 script subtag** is the documented, official mechanism

for script: `zh-Hant` (Traditional) / `zh-Hans` (Simplified). Script may combine with a region, e.g. `zh-Hans-US` is valid (language + script + region).

• Common errors:
• `eng` instead of `en` (ISO 639-2, not valid for hreflang)
• `jp` instead of `ja` (incorrect code for Japanese)
• `zh` is valid but ambiguous for script-specific pages; prefer `zh-Hans` or `zh-Hant` when targeting a script

5. Region Code Validation

• Optional region qualifier uses ISO 3166-1 Alpha-2 (e.g., `en-US`, `en-GB`, `pt-BR`)
• Format: `language-REGION` (lowercase language, uppercase region)
• A **country code alone is invalid**, you cannot specify a region without a

language (Google's own bad example is `be`, which is actually the Belarusian *language* code, not Belgium).

• Common errors:
• `en-uk` instead of `en-GB` (UK is not a valid ISO 3166-1 region code)
• `EU` / `UN` as a region (not valid ISO 3166-1 values)
• `es-LA` (Latin America is not a country; use specific countries)
• Region without language prefix

5b. Geo-targeting signal hierarchy

• Practical locale-signal heuristic: **ccTLD > hreflang annotations >

server location/IP > addresses/language/currency/Business Profile**. Do not present this as a confirmed Google ranking order. hreflang is a **hint, not a directive**. Google **ignores** locational meta tags and HTML geotargeting attributes.

• The Search Console **International Targeting report and the manual

country-targeting setting were removed in 2022**, do **not** recommend setting country targeting in GSC; hreflang is the remaining lever.

5c. Region-specific Search units (EEA, South Africa, Turkiye)

• Google documents Search experiences that exist only in certain countries:

**aggregator units**, **supplier units**, and carousels for hotel, flight, long-distance transport, and product queries shown to users in the EEA, South Africa, and Turkiye (documentation added 2026-09-08). Eligibility and participation are documented per unit; they are not ranking signals.

• When a site serves those regions with hreflang variants, note in the report

whether the business is an aggregator or a direct supplier and point to the regional documentation, so the client is not surprised by a different result layout in those markets.

6. Canonical URL Alignment

• Hreflang tags must only appear on canonical URLs
• If a page has `rel=canonical` pointing elsewhere, hreflang on that page is ignored
• The canonical URL and hreflang URL must match exactly (including trailing slashes)
• Non-canonical pages should not be in any hreflang set

7. Protocol Consistency

• All URLs in an hreflang set must use the same protocol (HTTPS or HTTP)
• Mixed HTTP/HTTPS in hreflang sets causes validation failures
• After HTTPS migration, update all hreflang tags to HTTPS

8. Cross-Domain Support

• Hreflang works across different domains (e.g., example.com and example.de)
• Cross-domain hreflang requires return tags on both domains
• Use Google Search Console verification for monitoring or cross-site sitemap submission when needed
• Sitemap-based implementation recommended for cross-domain setups

Common Mistakes

| Issue | Severity | Fix | |-------|----------|-----| | Missing self-referencing tag | Critical | Add hreflang pointing to same page URL | | Missing return tags (A→B but no B→A) | Critical | Add matching return tags on all alternates | | Missing x-default when fallback behavior is required | Medium | Add x-default pointing to fallback/selector page | | Invalid language code (e.g., `eng`) | High | Use ISO 639-1 two-letter codes | | Invalid region code (e.g., `en-uk`) | High | Use ISO 3166-1 Alpha-2 codes | | Hreflang on non-canonical URL | High | Move hreflang to canonical URL only | | HTTP/HTTPS mismatch in URLs | Medium | Standardize all URLs to HTTPS | | Trailing slash inconsistency | Medium | Match canonical URL format exactly | | Hreflang in both HTML and sitemap | Low | Choose one method (sitemap preferred for large sites) | | Language without region when needed | Low | Add region qualifier for geo-targeted content |

Implementation Methods

Method 1: HTML Link Tags

Best for: Sites with <50 language/region variants per page.

<link rel="alternate"